Air classifier



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A. H. STEBBINS AIR CLASSIFIE H Filed Feb. 1., 1.927

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A. H. STEBBINS AIR CLASSIFI ER Filed Feb. 1, 1927 2 Sheets-5116M 2 Jays MP we;

,4 TTO RNEY Patented Feb. 28, 1928.

ALBERT n. sTnB'Brns, or LOS ANGELES, CALIFORNIA.

AIR oLAssIrInn.

Application filed February 1, 1927. Serial No. 155,071.

This invention relates to multiple treatment air classifiers adapted for use 1n separating fine dust-like materials.

These fine dust-like particles are hard to separate because they tend to cling together and will not settle rapidly out ofthe air in which they are carried. It isthereforedesirable' to employ centrifugal force either alone, or in combination with gravity, to promote the separation of the very fine particles from the slightly larger particles, and in order to 'efiect a complete classification the materials should be subjected repeatedly to the separating forces. V

' The present invention is therefore dlrected to an air classifier which is so constructed that air bearing the materials to be treated is caused to travel along a tortuous path at high speed with the result that the heavier particles are thrown outwardly by centrifu gal force toward the outer wall of the loops or bends. This removes the larger particles from the air traveling near the. inner wall of the loops or bends so that the air and finer particles traveling near the inner curved wall of these loops or bends may be removed from the conduit without theheavier particles. In this manner the lighter particles are gradually removed from the conduit while the coarser particles remain therein throughout the classifying operation.

One of the features of the present invention resides in the construction whereby the size of the tortuous conduit having the loops or bends above mentioned is gradually decreased from oneend toward the other to accommodate the gradual decrease in the volume of the. air traveling lengthwise of the conduit. This decreasing in air volume is produced by withdrawing the air and finer particles traveling near the inside of the loops from the conduit while the larger particles remain in the. conduit for further treatment.

Another feature of the invention resides in the construction whereby two or more multiple treatment classifiers of the type that taper from one end toward the other are connected in series.

The various features of the invention and novel arrangement of parts will be best understood from the accompanying drawings when read in connection with the following description. v

In the drawingstire classifying operation is 'efiected. the tortuous conduit 10 which is shown as rig-.1 is a vertical sectional View through a classifier constructed n accordance with the present invent on i Fig. 2 is a rear elevation ofthe classifier ofFig l; w I Fig. "Si ls asectional view taken on the line 33 of Fig. 1;; j

Fig. 4 isavertical sectional a modified type of classifier; I I

Fig. 5 is a sidevi'ewof a portion of the classifier of Fig. .4, the sidewall being partly broken away; and 2 Fig. 6 is a vertical section view of a further modified construction. I

The classifier of. the present .inv'entionfis preferably supported in an upright position and may be operated either by suction or by.

an air blast, or by the combination of suction View through so I and air blast; but'in many casesthe useof suction alone will be desirable because if the materials being treated are carried lengthwise of the classifier by suctionthey will eX- ert a less wearing andcuttingaction upon the Walls thereof thanthey will if they are carried through the classifier'by an airblast.

The present invention may be given various embodiments, and one good construction is shown in Figs. 1, 2 and 3, wheremthe engradually decreased'in size from" its upper towards its lower or discharge end. In the construction shown the operation of the classifier is effected by exhausting air from the conduit 10 at various points along its length. conduit at its upper end where the materials to be treated are introduced into the. path of the air by the discharge hopper 11 having the adjustable gates 12 for controlling the rate of flow of'the materials to the conduit 10 from the feed hopper.

The conduit 10 is provided with a series of loops or bends, as will be apparentfroin the drawings,-and means is provided for ex-.

'hausting air fromthe conduit at the inner sideof these loops .or bends. In the construction shown the air exhaust means consists of'the p1pes 18 disposed at the inner This serves to draw air into the' Within. x

side of the; loops and arranged to extend transversely of the-tortuous conduit; Each exhaust pipe 13 has an air inlet opening or slot 14 disposed near the upper end of a passage-'15 leading from the lnner curved ortion ofv a loop or bend of the tortuous conmeans to be described, and this serves to draw air into the upper end of the conduit 10 through the air inlet openinglG; In o rder to prevent the materials from becoming clogged at the hopper 11 it may be desirable to provide the lower portion of this hopper with the air inlet apertures 17 which are arranged so that some of the air entering the conduit 10 will pass through the apertures 17 to promote the flow of materials into the conduit from the discharge end of the hopper.

Air is exhausted from the opposite ends of the exhaust pipes 13by providing the air exhaust receptacles 18 at the opposite sides of the conduit -10.f These receptacles are preferably made relatively large so'that the larger particles that enter these receptacles will have an opportunity to settle therein and collect in the lower ends 19 of each receptacle from which they may be withdrawn from time to time. Air is exhausted from the upper endsof the receptacles 18 by providing the exhaust pipe 20 which is connected to the reoeptaclesl18 by the branch pi es 21 and the pipe 20 leads to an exhaust. an 22. The rate :at'which the air is exhausted from the receptacles 18' may be controlled by'adjusting the gate or valve 23 mounted in the pipe 20. a V

. The air exhaust means described will cause the air and materials to be treated that enterthe upper end of the conduit 10 to travel lengthwise thereof at high-speed. This will cause the largerparticles to be thrown outwardly by centrifugal force towards the outer wall of the loops or bends 2 1, with the result that the larger particles are removed 7 from the air traveling near the inner wall of fsible to remove the and it is therefore posfiner particles from the classifier without removing thelarger particles by extractingfrom the classifier the the loops or bends,

' air and finer particles traveling near the inner wall of the loops of the conduit. Since air is exhausted from the conduit'lO at various pointsalong its length the volume of air within the conduit will gradually decrease towards the lower end of the classithe air within'the conduit. The larger particles fier. It may therefore be desirable to give the conduit the tapered construction shown so that it gradually decreases in size from its upper to its lower end to accommodate gradual decrease in the volume of the which remain within the conduitthroughout the treatment are discharged at the ,lower end 25thereof into the closed receptacle 26 which may extend a substantial distance downwardly below the discharge end of the conduit, asrshown and portions of this re ceptacle mayalso extend upwardly at-either side of the tortuous conduit, as willbe 'ap lower end of the discharge parent from Fig. 1. The air which enters the'receptacle 26 through the discharge opening 25 with the larger particles may be removed from the upper end of the receptacle 26 by providing the exhaust openings 27 which lead into the exhaust receptacles 18 disposed at the opposite sides of the conduit. By making the receptacle 26 relatively large as shown the heavier particles will have ample opportunity to collect in the lower: end 28 thereof so that they may be withdrawn from time to time. p

The entire air classifier may be constructed of sheet metal and the tortuous conduit 10 may be formed by providing the tortuous walls 24: the marginal edges of which may be secured tothe inner side walls 29 of the receptacles 18 and these receptacles may be provided with the outer side walls 30; The opposite ends of the exhaust pipes 13 extend through the inner side walls 29 andthese. pipes, may be formed by, giving them the. spiral construction shown, wherein it will be seen that each pipe has the curved portion 31 which forms part of the tortuous conduit and also forms the upper wall of the air ex: haust passage 15. It may be desirable to omit the exhaust slot from the uppermost pipe-32 of the conduit and the same is true of the pipe 32 adjacent the lowerend of the conduit 10. l

The distance between theadjacent pipes 13 near the lower end of the conduit will be quite small, say not over two inches apart, and the distance between the pipes 13 near 9 the upper end of the conduit may not be more than several inches so that the successive loops or bends 2 1 of the conduit will be relatively small','and a conduit having a large number of loops or bends may be provided 1 within a classifier that is only a few feet in height. It will therefore be seen that a large number of successive treatments may be effected-in a relatively small classifier. 3

If it should be desired to subject the ma- 0 1, but are directed into a secondtortuous classifier 33 which may be similar in construction to the classifier through which'they have just passed. Air, for carrying the materials'through the second'tortuous" conduit 1 33 maybezintroduced throughthe air inlet passage 34 and air may be exhausted from the entire series. of exhaust pipes 13 of Fig.

4; by providing the upper portion of this classifier with the exhaust receptacles 18.the

lower ends of which receptacles are connected to the exhaust receptacles 35. a

It will be understood from the foregoing description'and from the drawings that air from the atmosphere is introduced into the tortuous conduit only at the upper end thereof and is not introduced at various points lengthwise of the conduit, with the result that a closed construction is provided which might well be connected to a dust producing device from which it is desired to ex haust dust-laden air. Having this use of the present invention in mind a modified construction is shownin Fig. 6 wherein the feed hopper 11 has been omitted, and the upper end of the tortuous conduit 10 is provided with a feed or suction pipe 36 which may lead from the upper portion of a concentrator deck or from various other dust-producing devices.

A multiple treatment classifier having the p construction herein described, while small- 7 and compact, has a largecapacity due to the continuous flow of air andmaterials to be treated through the tortuous conduit at high speed, and it utilizes the separating action of centrifugal force to a high degree considering the small size of the loops of the conduit. The operation of this novel classifier requires verylit-tle attention on the part 'of the machine attendant, and the large number of treatments to which the materials may be subjected serve to completely remove the finer from the slightly larger particles, while the high speed at which the air and materials travel within the conduit prevents clogging.

While the multiple treatment classifier of the present invention is designed more particularly for the use of air as a carrying medium for the particles to be separated, and the specification and claims are directed to the air treatment, nevertheless water may be successfully employed as the carrying medium in a classifier having the novel construction of the present invention. When water constitutes the carrying medium the stream of water and ore pulp will pass down- Wardly in the tortuous passage 10 and if this relatively heavy carrying medium exercises a substantial floating or semi-floating effect on the lighter materials to be separated from the heavier materials, then the water lying atthe uppersurface of the stream traveling within the passage and the floating particles may be removed through the discharge slots 14, while the heavier particles which do not rise to the surface will be delivered as tailings into the hopper 2'6.

What is claimed is 1. A multiple treatment classifier, comprising in combination, a tortuous conduit 7 that gradually decreases in size fromone end toward the other and provided with a series of bends or loops, means for introductraveling within the conduit.

ing air ia nd the materials. to be treated into the larger end of the conduit to travel lengthwisethereof at high speed so that the heavier particles will be thrownoutwaroliy by centrifugal force toward the outer wall of the loops, exhaust pipes mounted transversely of said conduit within-the bends/of the loops and provided with longitudinally extending slots arranged to exhaust from the conduit the air traveling near the inner wall. of: the loops and from which the heavier particles have been removed by centrifugal force, and each slot being positioned to face away from the main path'of the air 2. A classifying unit consisting of a plurality of multiple treatment classifiers con nected in series so that one classifier discharges into the next to retreat the mate rials, and each classifier, comprising in combination, a tortuous conduit'that gradually decrease'sin size from one end toward the other and provided with a series of bends at the inner side of the loops the air which has been freed from the, by centrifugal force. p

3. A multiple treatment classifier, comprising in combination, a tortuous conduit having a series of bends or loops, exhaust heavier particles pipes extending transversely of the conduit; and arranged to exhaust air adjacent the inner wall of the loops or bends, air exhaust receptacles disposed at the opposite sides of the conduit for exhausting air from said pipes andconduit, means for introducing air and the materials to be treated'into the upper portion ofthe conduit to travel lengthwise thereof at high speed so that the heavier particles will be thrown outwardly by centrifugal force toward the outer wall of said loops, and a closed receptacle for receiving the heavier particles di'scharged from the lower end of said conduit;

and provided with settling compartments that extend along the conduit adjacent its remaining two sides;

4:. A multiple treatment classifier, comprising in combination, a tortuous conduit that gradually decreases in size from one; end toward the other and provided with a series of bends or loops, means for introducing air and the materials to be treated into the larger end of the conduit to travel lengthwise thereof at high speed so that the heavier particles will be thrown outwardlyby centrifugal force toward the outer wall of the loops, exhaust pipes mounted ings transversely of said conduit Within the transversely ofthe conduit, withinfthe loops and each pipe having an inlet opening formed in its upper side and, a settling passage=leading from the innerourved side of theconduit to said opening, means. for introducing air and the materialsto betreated .into the larger end. vof the. conduit to travel lengthwisethereof at high speed so that the :heavier vparticles will be thrown outwardly by centrifugal force toward the outer Wall of the loops, and means for exhaustingair from said pipes. In testimony whereof, I have signed my 'name to this specification. v

: ALBERT H. sTEBBIus, 

